Peracid compositions have been reported to be effective antimicrobial agents. Methods to clean, disinfect, and/or sanitize hard surfaces, meat products, living plant tissues, and medical devices against undesirable microbial growth have been described (e.g., U.S. Pat. No. 6,545,047; U.S. Pat. No. 6,183,807; U.S. Pat. No. 6,518,307; U.S. Pat. No. 5,683,724; and U.S. Patent Application Publication No. 2003/0026846). Peracids have also been reported to be useful in preparing bleaching compositions for laundry detergent applications (U.S. Pat. No. 3,974,082; U.S. Pat. No. 5,296,161; and U.S. Pat. No. 5,364,554).
Peroxycarboxylic acids can be prepared by the chemical reaction of a carboxylic acid alkyl ester and a peroxide reagent, such as hydrogen peroxide (see Organic Peroxides, Daniel Swern, ed., Vol. 1, pp 313-516; Wiley Interscience, New York, 1971). However, under slightly basic to acidic pH (from about 8 to about 4), the reaction often does not proceed rapidly enough to produce a peroxycarboxylic acid concentration that is suitable for many commercial disinfecting and/or bleaching applications.
One way to overcome the disadvantages of chemical peroxycarboxylic acid production is to use an enzyme catalyst having perhydrolysis activity. U.S. patent application Ser. No. 11/638,635 and U.S. Patent Application Publication Nos. 2008/0176783; 2008/0176299; and 2009/0005590 to DiCosimo et al, disclose enzymes structurally classified as members of the CE-7 family of carbohydrate esterases (e.g., cephalosporin C deacetylases [CAHs] and acetyl xylan esterases [AXEs]) that are characterized by significant perhydrolysis activity for converting carboxylic acid esters (in the presence of a suitable source of peroxygen, such as hydrogen peroxide) into peroxycarboxylic acids at concentrations sufficient for use as a disinfectant and/or a bleaching agent. Some members of the CE-7 family of carbohydrate esterases have been demonstrated to have perhydrolytic activity sufficient to produce 4000-5000 ppm peracetic acid from acetyl esters of alcohols, dials, and glycerols in 1 minute and up to 9000 ppm between 5 minutes and 30 minutes once the reaction components were mixed (DiCosimo et al., U.S. 2009/0005590). The enzymatic peracid generation system described by DiCosimo et al. in each of the cited patent application publications may be based on the use of multiple reaction components that remain separated until the peracid solution is needed.
It has been observed that, when using a multi-component system comprising a first enzyme catalyst/substrate component and a second component comprising an aqueous source of peroxygen, the use of one or more substrates that are insoluble or partially insoluble in water after mixing of the two components can result in at least three conditions that interfere with the ability to efficaciously produce and deliver a peroxycarboxylic acid product: first, the viscosity of the enzyme catalyst/substrate constituent can be too high to permit efficient mixing with a second constituent comprising a source of peroxygen, which decreases the rate of production of peroxycarboxylic acid; second, the viscosity of the enzyme catalyst/substrate constituent can be too high to permit certain modes of delivery of a product comprising a mixture of the enzyme catalyst/substrate constituent and the source of peroxygen, such as spraying; third, the dissolution rate of the substrate in the enzyme/substrate component after mixing with a second component comprising a source of peroxygen in aqueous solution is too low to permit a satisfactory rate of production of peroxycarboxylic acid. These problems also become evident in situations where use of a particular ratio of a component comprising an aqueous source of peroxygen to a component comprising an enzyme catalyst/substrate constituent is desired. As such, commercial uses of multi-component systems that involve the storage of the enzyme catalyst having perhydrolysis activity and substrate separately from a source of peroxygen until a desired time of reaction have remained impracticable for some applications.
The problem to be solved is to provide a method to enzymatically produce peracids when using a multi-component generation system characterized by at least one first component comprising a formulation of a carboxylic acid ester substrate and an enzyme catalyst comprising a CE-7 carbohydrate esterase having perhydrolysis activity, wherein the carboxylic acid ester substrate is (1) partially or substantially insoluble in an aqueous matrix, and/or (2) slow to dissolve into an aqueous reaction matrix and/or (3) has a viscosity that does not facilitate easy mixing for some commercial applications (e.g., use of a two compartment spray bottle designed to mix two liquid components having different viscosities and/or solubilities), and additionally characterized by at least one second component comprising an aqueous solution comprising a source of peroxygen (e.g., an aqueous formulation of hydrogen peroxide).